The present invention relates to an apparatus for interconnecting rotary shafts, and more particularly to a shaft connecting apparatus suitable for use as power transmission means for the rolls of rolling mills.
With a rolling mill as shown in FIG. 1, a plurality of rolls B.sub.1, B.sub.2, B.sub.3, B.sub.4 arranged in a row are driven by single drive means A through drive spindles C.sub.1, C.sub.2, C.sub.3 interconnecting the drive means and the rolls. Since the spacing L between the adjacent rolls in this arrangement is very small, couplings a as shown in FIGS. 2 and 3 are usually used in the interconnecting drive spindles C.sub.1, C.sub.2, C.sub.3 to connect a drive shaft b, a driven shaft c and an intermediate shaft d together.
In the case of such rolling mills, the level of the roller during rotation undergoes delicate variations, so that the shafts b, c, d of the drive spindle must be adapted for angular displacement. For this purpose, clearances S.sub.1 are provided between the couplings a and shafts b, c, d fitting therein, while clearances S.sub.2 are also provided between the opposed ends of the shafts b, c, d. However, when the shafts are thus loosely fitted in the couplings, the intermediate shaft d during the rotation of the drive shaft undergoes vibration in the direction of the rotation and oscillation in the axial direction, giving rise to wear on the surfaces of the coupling a and the shafts b, c, d in fitting contact with each other. Moreover, the vibration and oscillation will be delivered to the rolls and other portions of the rolling mill, consequently reducing the accuracy of the rolling operation and causing damage to the mechanical parts early. Presumably, these problems can be overcome if the intermediate shaft d is provided, as its opposite ends, with universal joints of the trunnion type which permit a free angular displacement, such that fitting yokes on the universal joints are connected to the drive shaft b and to the driven shaft c, but this arrangement renders the drive spindle excessively great in its overall length and is not usable in rolling mills in which the roll-to-roll spacing L is limited as already stated.